This invention relates; to a stable, fluid suspension of an abrasive material, a process for preparing such suspension, and the use thereof in dentifrices
Prior to the present invention, it was difficult to suspend abrasive materials for use in the dentifrice industry and consequently the amount of abrasive material in wet compositions was inconsistent. The normal manner of using the abrasive was to suspend it in water and then mix it with the other components. In this manner, especially when high volumes of abrasive were used, the abrasive would some times settle out causing the amount of abrasive in the final composition to vary from batch to batch. Another option for getting the abrasive in the final dentifrice composition was to use a dry powder abrasive. Although this produced consistent compositions, dusting problems were often experienced resulting in a longer toothpaste production process. The longer preparation time is due to the fact that the abrasive, such as calcium carbonate, had to be added slowly over a certain period of time to minimize dusting as well as agglomeration of finely divided particles upon contact with the dentifrice gel premix. Dusting also created safety and health hazards by making the floor where the composition was being prepared slippery so that accidents could occur. Also, this dusting was a health problem for the workers who had to inhale this dust creating respiratory problems.
For the above reasons, plant operators desire a fast, effective, consistent, and simple way to incorporate abrasives into a dentifrice system. In other words, to reduce production costs as well as dusting in current toothpaste production, it is desirable to deliver a slurry or a fluid system (i.e., suspension or dispersion) of the abrasive. The use of such a slurry or fluid system will also allow manufacturers to use a continuous and/or batch production process that is efficient.
The present invention is directed to a fluid suspension consisting essentially of a) an abrasive, b) a suspending vehicle, and c) a water-swellable or water-soluble polymer.
The present invention also relates to a method of making a fluid suspension comprising dispersing and hydrating a polymer in a suspending vehicle of water or polyhydric alcohol or mixtures thereof and adding an abrasive to form the fluid suspension. Also, this system can be prepared in the reverse order by adding the abrasive to the suspending vehicle and then adding the polymer thereto. The fluid abrasive suspension can also be prepared by mixing in dry form a polymer and a abrasive to form a mixture and then adding a suspending vehicle of water, polyhydric alcohol, or mixtures thereof to said mixture and stirring to form the fluid suspension. Also, the fluid suspension can be prepared adding the ingredients in the reversed order, i.e., mixing the polymer and the abrasive, either together or alone, into the suspending vehicle.
The present invention also comprehends a method of making a dentifrice comprising adding to the above mentioned fluid abrasive suspension composition the desired dentifrice formulation ingredients. Again, the reverse order of addition can be used in that the desired dentifrice formulation ingredients can be added either alone or together to the fluid abrasive suspension mentioned above.
It has been surprisingly found that abrasives could be made into stable fluid suspensions for a more efficient and consistent handling and use in the dentifrice industry. These suspensions have a long shelf life and thus can be shipped or pumped without the problems associated with settling. Another advantage of these fluid abrasive suspensions (FAS) is that since these FAS are made up of ingredients that are used in dentifrice, they are compatible and do not use ingredients that would be superfluous to dentifrice.
In accordance with this invention, the terms xe2x80x9csuspensionxe2x80x9d and xe2x80x9cdispersionxe2x80x9d are used interchangeably to mean a system in which solid particles, the abrasive, are dispersed or suspended in a suspending vehicle of water or polyhydric alcohol or mixtures thereof to form a stable dispersion. Also, a xe2x80x9csolutionxe2x80x9d is a homogeneous, single-phase mixture of a solvent such as water and a soluble material that is completely dissolved in the solvent. A xe2x80x9cslurryxe2x80x9d is defined as a liquid and an insoluble, solid material that forms a flowable mixture (such as mud or plaster of Paris).
A dentifrice is commercially available in four forms: powder, paste, gel, and liquid. The present invention is directed to all of the forms except powder. These forms are generally referred to as toothpaste. Hence, in this invention, the terms xe2x80x9cdentifricexe2x80x9d and xe2x80x9ctoothpastexe2x80x9d will be used interchangeably.
The fluid abrasive suspension (FAS) of the present invention includes an abrasive, a suspending vehicle, and a water-swellable or water-soluble polymer. The FAS may also contain at least one other ingredient that may be used in dentifrices such as perservatives, fluoride, buffering agent, humectant, coloring agent, flavor, sudsing agent, detergent, salts, tartar control, sweetener, vitamin, whitening agent, antiplaque agent, anticalculus, sequestering agent, and odor removers.
Unless otherwise mentioned, all of the amounts in the FAS are based on the total weight of the FAS.
In accordance with the present invention, the FAS contains a lower limit of the abrasive of 5 weight percent on the total weight of the FAS, preferably 15 weight percent, and more preferably 30 weight percent. The upper limit in the FAS is 70 weight percent, preferably 60 weight percent, and more preferably 45-weight percent. In toothpaste, abrasives of various types can provide the unique benefits of exceptional dental cleaning and polishing performance without unduly abrading tooth enamel or dentin. The abrasive materials must also be exceptionally compatible with sources of soluble fluorides. Hence, it is important that the correct amount of abrasive be in the toothpaste so that it can perform its intended purpose well.
In accordance with this invention, the bulk density of the abrasive polishing material should be in a specific range. If the bulk density is too low, it becomes more difficult to incorporate the abrasive into the suspension system. If the bulk density is too high, it becomes impractical to handle and use. Hence, there is a desirable range that should be used. This makes it easy for processing and pumping the abrasive from one stage to the next in the making of a dentifrice formulation. The lower limit of the bulk density is about 0.2 gram per milliliter (g/ml), preferably 0.4 g/ml, and more preferably 0.6 g/ml. The upper limit of the bulk density is about 1.2 g/ml, preferably 1.0 g/ml, and more preferably 0.8 g/ml.
Examples of abrasive materials that can be used in this invention are calcium carbonate, calcium phosphate, sodium meta phosphate, sodium bicarbonate, calcium pyrophosphate, dicalcium phosphate, silica, and alumina. The preferred abrasives are calcium carbonate, especially precipitated calcium carbonate (PCC), dicalcium phosphate (Dical), and silica.
In accordance with the present invention, the suspending vehicle of the FAS can be water, a polyhydric alcohol, or mixtures thereof. Water used in this invention should preferably be deionized or demineralized and free of organic impurities. When water is used alone in the FAS, it should have a lower limit amount of 25% by weight of the FAS formulation, preferably 35% and more preferably 45%. The upper limit for the water should be 90%, preferably 75% and more preferably 60%.
Some examples of the polyhydric alcohols which can be used with water are: sorbitol, glycerol, propylene glycol, polyethylene glycol, ribitol, xylitol, mannitol, poloxamer, and mixtures thereof.
The anhydrous polyhydric alcohols (PHALC) which can be used alone for FAS without presence of water are: propylene glycol (PG), polyethylene glycol (PEG), glycerol (G), and poloxamer (PXMR). For example, PG and PEG can be used with Klucel(copyright) polysaccharide and G can be used with Natrosol(copyright) product. These PHALC could also be used in combination with the other polyhydric alcohol mentioned above such as xylito, manitol, etc.
When the polyhydric alcohol is used alone in the FAS formulation, it should have a lower limit of about 25 wt %, preferably 30 weight percent, and more preferably 45 wt %. The upper limit amount can be about 90-wt. % preferably 75 wt % and more preferably 60 wt %.
In the present invention, when water and polyhydric alcohol are used in combination in the FAS, the amount of the combination should be about at least 25 wt %. The upper limit should be about 90 wt %, preferably 75 wt %, and more preferably 60 wt %. Preferred mixtures are water with sorbitol or glycerol with sorbitol or water, sorbitol and glycerol.
The polymer is the ingredient that provides stability to the FAS. Examples of the polymers that can be used in this invention are polysaccharides such as carrageenan, pectin, carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), hydroxypropylcellulose (HPC), ethylhydroxyethylcellulose (EHEC), methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), xanthan gum, inorganic gelling or thickening agents such as clays (i.e., magnesium aluminum silicate), silica, silica precipitate, silica aerogel, pyrogenic silica, homo- or copolymer of acrylic acid or acrylic acid salt, polyvinylpyrolidene, gelatin, and mixtures thereof. The amount of tea polymer in the FAS can have a lower limit of about 0.1 wt % based on weight of the FAS, preferably 0.5 wt %, and more preferably 1.0 wt %. The upper limit amount is about 10 wt %, preferably 7.0 wt % and more preferably 3.0 wt %.
In accordance with the present invention, toothpaste compositions contain an abrasive, a humectant, a fluoride ion source, a buffering agent, a detergent, and water. The humectant serves to keep the toothpaste composition from hardening upon exposure to air and provides freeze-thaw stability. Certain humectants can also impart desirable sweetness or flavor to toothpaste compositions. The humectants, on a pure humectant basis, generally comprise from about 5 wt % to about 80 wt %, preferably from about 20 wt % to about 35 wt % of the total toothpaste composition. Examples of humectants are the suspending vehicle, mentioned above.
The fluoride ions combine with dental enamel and thereby reduce enamel solubility in acid. The applying of fluoride ion to dental enamel protects teeth against tooth decay. The fluoride ion has to be present in the amount of from about 0.01 wt % to about 3.0 wt %, preferably from about 0.03 wt % to about 1.0 wt % of the toothpaste composition.
A buffering agent is used to adjust and maintain the toothpaste composition at the desired pH, which is generally in the range of 3.0 to 11.0, preferably 6.0 to about 9.0. Examples of buffering agents are phosphates and tris(hydroxymethyl)-aminomethane with water-soluble phosphate salts being preferred.
Detergents are used to produce suds in order to remove stains and foreign particles from the teeth and gums. Generally, detergents can be used in the toothpaste from about 0.2 wt % to about 3.0 wt %, preferably from about 0.75 wt % to about 1.5 wt %. Examples of detergents are sodium lauryl sulfate and sodium lauryl sarcosinate.
In addition to the above mentioned preferred ingredients, the toothpaste composition may optionally contain binding agents, sudsing agents, flavoring agents, sweetening agents, anticalculus agents, film formers, antiplaque agents, coloring agents, whitening agents, odor remover agents, breath fresher, vitamins, sequestering agents, salts, tartar control agents, pain killers, preservatives, and pigments.
Toothpaste of the present invention is prepared by mixing together in any order or by any conventional means the preferred and optional components herein.
In accordance with the present invention, a method of making a dentifrice comprising mixing a thickening agent, water, and a polyhydric alcohol to form a solution and adding to this solution the above mentioned fluid abrasive suspension composition. Also, any of the optional ingredients can be added as desired by the manufacturer. The normal pH range of toothpaste is about 3.0 to about 11.0, preferably 6.0 to 9.0. Other methods of making toothpaste are to add all of the ingredients individually or pre-blended as desired to the FAS or add the FAS to the preferred and optional ingredients in any order of addition.